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Ironmasters of Coalbrookdale: 18th century

Until the early 18th century the working of iron has been restricted by a practical consideration. The smelting of iron requires large quantities of charcoal, with the result that ironworks are usually sited inaccessibly in the middle of forests. And charcoal is expensive.

In 1709 Abraham Darby, an ironmaster with a furnace at Coalbrookdale on the river Severn, discovers that coke can be used instead of charcoal for the smelting of pig iron (used for cast-iron products). This Severn region becomes Britain's centre of iron production in the early stages of the Industrial Revolution. Its pre-eminence is seen in the Darby family's own construction of the first iron bridge, and in the achievements of John Wilkinson.

Ironbridge: 1779

In the space of a few months in 1779 the world's first iron bridge, with a single span of over 100 feet, is erected for Abraham Darby (the third of that name) over the Severn just downstream from Coalbrookdale. Work has gone on for some time in building the foundations and casting the huge curving ribs. But in this new technology little time need be spent in assembling the parts - which amount, it is proudly announced, to 378 tons 10 cwt. of metal.

The lightness of the structure strikes all observers. An early visitor comments: 'though it seems like network wrought in iron, it will be uninjured for ages.' It is uninjured still. A great tradition, bringing marvels such as the Crystal Palace, begins in this industrial valley.

Puddling and rolling: 1783-1784

In successive years Henry Cort, an ironmaster with a mill near Fareham in Hampshire, patents two processes of lasting significance in the story of metallurgy.

One is the technique which becomes known as puddling, for which Cort patents a machine in 1784. Cort's innovation is a furnace which shakes the molten iron so that air mingles with it. Oxygen combines with carbon in the metallic compond, leaving almost pure iron. Unlike the brittle pig iron (or cast iron), this purer metal is malleable. Capable of being hammered and shaped, it is a much more useful metal in industrial processes than cast iron.

In the previous year Cort has also patented a machine for drawing out red-hot lumps of purefied metal between grooved rollers, turning them into manageable bars without the laborious process of hammering. His device is the origin of the rolling mills which subsequently become the standard factories of the steel industry.

Cort's subsequent career exemplifies the risks involved in the entrepreneurial excitements of the Industrial Revolution. After spending all his own money on his inventions, he raises further capital from the deputy-paymaster of the navy. It turns out to have been embezzled. Cort is ruined before his inventions bring him a profit.

This History is as yet incomplete.

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